Hello, & welcome to the forums! However, many things mentioned here have already been suggested. There are definitely updates planned for the Arcade, with the addition of a new game called “Block Party” being one that has already been confirmed.
For sumoing, I would recommend to create a custom server with your friends, or by asking people if they’d like to sumo. You can create a custom server with the /cs command. Skyblock is something that would likely not be added, as the Hive has always been a mini-game server. UHC has already been suggested, and you can vote on this here: New Game Suggestion: UHC
Thanking you for taking the time to create and make a suggestion! 